I think I can beat your record - I saw someone cycling after dark, wearing dark clothing (no helmet), on the wrong side of the road, coming out of a T-junction (so that traffic on the main road wouldn't see him coming) ... with someone else sitting on his handlebars (dressed the same way as him).

Fortunately I was able to swerve around them in time (on my motorbike), but I'm mainly glad because a collision would have been inconvenient for me; I'd have no sympathy for them if they got hit by someone else.